Air pollution from ships Online version

Air pollution from ships
- Could advantageously be reduced

Text from pamphlet published jointly by The Swedish NGO Secretariat on Acid Rain, European Environmental Bureau (EEB), and European Federation for Transport and Environment (T&E).

Revised version January 2002.

Also available in pdf format (900 kB)

Introduction
In certain environmental aspects, ships have definite advantages over land-based modes of transportation. They call for little in the way of infrastructure and can transport large volumes of freight with a low expenditure of energy.

Nevertheless they pour out great quantities of pollutants into the air in the form of sulphur and nitrogen oxides. There are however technical means by which these emissions could be reduced by as much as 80-90 per cent, and very cost-effectively compared with what would have to be done to achieve similar results ashore.

Here follows an examination of the problems that are involved and the technical and political possibilities for solving them.

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Sea vs land
The emissions of air pollutants from ships engaged in international trade in the seas surrounding Europe - the Baltic, the North Sea, the northeastern part of the Atlantic, the Mediterranean, and the Black Sea - were estimated to have been 2.8 million tons of sulphur dioxide (SO₂) and 4.0 million tons of nitrogen oxides (expressed as NO₂) a year in 1990. This would mean that shipping then accounted for 7 per cent of the European total for sulphur and 15 per cent of that for nitrogen oxides. But if emissions from land-based sources in Europe continue to fall as at present envisaged, and those at sea remain unchanged, by 2010 the proportions from shipping will rise to 17 and 23 per cent respectively. See table below.

When the fifteen EU member countries have fulfilled their commitments in accordance with the directive on national emission ceilings, and assuming that emissions from shipping remain at their 1990 level, by 2010 the latter will be equivalent to three-quarters of the EU total for sulphur and nearly two-thirds of that for nitrogen oxides.

It should be noted that these figures, high as they are, refer only to ships in international trade. They do not include emissions from shipping in countries' internal waterways or their territorial offshore waters, which are given in the domestic statistics of each country. Moreover, between 1990 and 1999 the intra-EU transports of freight by sea increased by 273 million tonkilometres, or 30 per cent, and ship's movements are expected to go on increasing.

European emissions of SO₂ and NOx in 1990 and projections for 2010. Millions of tons.

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Cost-effective to do it at sea
The costs of typical measures for reducing the emissions of sulphur and nitrogen oxides from ships range respectively from 0.5 to 1.2 and 0.35 to 0.60 euro per kilogram. The measures required for reducing the emissions of nitrogen oxides from sources on land more than at present would usually cost still more, and in some cases much more.

A main reason for the costs at sea being lower is that the easiest and least expensive measures have already been taken ashore, but not yet at sea.

The cost-effectiveness of abatements at sea was studied by IIASA, the International Institute for Applied Systems Analysis, while examining the EU strategy for combating acidification. It appeared that if the interim target for environmental quality proposed for the EU were to be attained solely by the use of technical measures on land, the annual cost by 2010 would be around 7 billion euro. The overall cost could however be brought down by 2.1 billion euro, or about 30 per cent, if cost-effective measures to limit the emissions of sulphur and nitrogen oxides from ships were applied in the Baltic, North Sea, and waters of the northeastern Atlantic. (No account was taken of emissions in the Mediterranean.)

With measures for shipping added to those for land-based sources, the environmental target could thus be attained at a considerably reduced cost. Alternatively, still more could be achieved at the same cost.

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Measures: Debated and started
Although some countries have taken steps to attack the problem of ships' emissions independently, on the whole little has been done about it.

International
Shipping being largely an international business, it would be logical to try and bring about global agreement for control of its emissions, and an attempt has been made in the Marine Environment Protection Committee of the UN International Maritime Organization, IMO. After years of negotiation, agreement was reached in the autumn of 1997 on an air-pollution annex to the MARPOL 73/78 Convention. But this agreement was so weak that it was obvious it would have little effect. The voting rules of the convention, as well as experience to date, in any case make it unlikely that further moves can be expected from the IMO in any foreseeable future.

Protocols for reducing emissions under the Convention on Long-range Transboundary Air Pollution do not cover those from international shipping. Although it has long been held within the European Union that shipping is a matter for the IMO, the Commission has recently been employing a consultant to study the economic, legal, environmental, and practical implications of an EU system for reducing the emissions of SO₂ and NOx from ships. The EU directive on national emission ceilings requires the Commission to present a program of action for reducing emissions from international maritime traffic before the end of 2002.

National moves
Fairway dues, differentiated for environmental effect, have been charged in Sweden since January 1998 (see box). The harbour dues are also differentiated at most Swedish ports, and all the major ones - although in this case the port authorities all act independently and use rates to attract trade, so there is less differentiation than for the nationally agreed fairway dues.

A rapid increase in the number of ships operating on low-sulphur oil, spurred to some extent by the demands for environmentally friendly transport from some of the big shippers, has come about since 1998. By December 2000 some 1450of the 3500 ships calling regularly at Swedish ports were running on low-sulphur oil, although some of them had already begun to do so before the system started.

The response has not been so marked in regard to NOx emissions. As of October 2001, applications for reduction of the fairway dues had only been made for about thirty ships. Despite that relatively low number, the annual emissions of NOx are estimated to have fallen by 27,000 tons, and the number of cleaner ships is expected to gradually increase. The difference can be explained as follows: Whereas the cost of switching to low-sulphur fuel is regarded as moderate and its implementation easy, reducing NOx emissions requires a larger investment and so the question of profitability enters. The incentive should however be greater if more countries were to introduce a system of environmentally differentiated dues.

A weakness of the Swedish system is that it takes no account of the distance travelled - which greatly affects the amounts of pollutant. Ships making only short trips thus pay relatively more than others travelling longer distances between ports - a disadvantage that is however partly offset by discounts to frequent callers. One way of making the dues really correspond with emissions would be to take into account the distance travelled from the last port of call, while abandoning favourable treatment of frequent visitors.

Harbour dues differentiated according to ships' emissions of sulphur and nitrogen oxides have now been introduced at Mariehamn on the Åland Islands, and in Finland and Germany the ports of Helsinki and Hamburg allow lower dues for ships using fuel with less sulphur. An environmentally differentiated tonnage tax has recently been introduced in Norway, but it offers weaker incentives to reduce emissions than the Swedish system.

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The means are available
The technology already exists for cost-effective reduction of the emissions of sulphur and nitrogen oxides from ships.

Sulphur
Emissions are directly proportional to the sulphur content of the fuel. The simplest and least expensive way of reducing them is to go over to using bunker oil with a low sulphur content. The average sulphur content is now around 3 per cent, but low-sulphur oils can also be had. They require no engine modification, and the additional cost is no more than marginal. For oils with a sulphur content of 1 and 0.5 per cent it is around $l0 and $30 per ton (at present high-sulphur oil costs around $130 per ton). Because of its higher quality, low-su1phur oil also has the advantage of making for smoother engine running, with less risk of operating problems.

Nitrogen oxides
There are various methods for reducing NOx emissions, differing somewhat in cost and effectiveness.

Water injection and water emulsion. Water is injected into the combustion chamber or mixed with the fuel in order to lower the temperature of combustion and hence reduce NOx formation. The potential for emission reduction is at most around 50 per cent, but at the cost of increased fuel consumption. The installation cost is however lower than for either of the following methods.

HAM, Humid Air Motor, is a technique for preventing the formation of NOx during combustion by adding water vapour to the combustion air. Performance is unaffected either by the quality of the bunker oil or by engine workload. By reducing the consumption of fuel and lubricating oil, HAM has the advantage over SCR of somewhat lowering operating costs instead of increasing them. The method is able to reduce NOx by 70-80 per cent at a cost apparently similar to that of SCR.

Selective Catalytic Reduction, SCR, is a system for after-treatment of the exhaust gases. It can reduce the emissions of nitrogen oxides by more than 90 per cent, but may require low-sulphur bunker oil. When retro-fitted it replaces the exhaust silencers. Nitrogen oxides are reduced to nitrogen gas by spraying urea or ammonia into the gases before they pass through a catalytic converter. Reduction costs are generally below 0.6 euro per kg NOx, lower if the equipment can be installed while the ship is being built. There are now more than fifty ships fitted for SCR. About half of them are Swedish, and most of the others are frequent callers at Swedish ports.

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Recommendations
All European countries would stand to gain from a reduction of the emissions of sulphur and nitrogen oxides from ships, since it could cut down the overall cost compared with that for reduction through measures applied to land-based sources only. The following measures are proposed:

• The best approach would be to combine regulation with market-based instruments, say, economic incentives.
• The EU should introduce legislation for reducing the emissions of SO₂ from ships - either by setting limits on the sulphur content of fuel consumed in territorial waters (or preferably in the "exclusive economic zones"), or on the sulphur content of fuel sold in EU ports, or both. The maximum permitted content for bunker fuel should initially be 0.5 per cent.
• Since the EU legislative process is likely to take some years, and most probably will cover only parts of the problem, charges should be imposed that are differentiated for environmental effect and apply impartially to all vessels.
• Because methods of charging shipping dues vary, the EU should adopt a directive to make all member states as well as candidate countries that have not already done so introduce fairway dues that preferably take account of the distance travelled. It would be better to introduce differentiated fairway dues than to try and superimpose differentiation on existing harbour dues, since fairway dues can be made non-negotiable and completely transparent.
• In its White Paper on infrastructure charging the EU Commission "recognizes the need" for a pricing system based on marginal costs, including those for damage caused by exhaust emissions. If applied to all forms of transportation, it would encourage introduction of fairway dues in all EU states with a seaboard. But as long as competing modes do not pay their environmental costs, the charges on shipping should be differentiated in such a way as to be revenue neutral.
• Charges should be related to the amounts of pollutant emitted, and set so as to make it financially worthwhile - at least for ships that regularly frequent the area - to change over to the use of low-sulphur fuels and to invest in the technology needed to ensure a distinct reduction of NOx emissions.
• If a common charging system should appear impossible of achievement, the next-best solution would be for seaboard countries to introduce differentiated fairway and harbour dues independently, but on the lines of the Swedish. Although the effectiveness of the Swedish system is somewhat eroded by the fact that it takes no account of distance and allows various kinds of discount, the combined effect on emissions of more countries taking part should nevertheless be significant.
• The EU and its member states should make every effort to ensure the early entry into force and subsequent implementation of the Annex VI to the MARPOL Convention. They should also strive to markedly strengthen the weak emission standards for NOx in the Annex.
• Because of the legal difficulties of introducing strict NOx emission standards for ships in the EU, and the size of the capital investments needed for the abatement of NOx, it may be useful to investigate the possible use of tradeable emission permits. Land-based emission sources with high marginal costs for reductions could for instance be allowed to buy emission permits from ships plying in nearby waters, provided the shipowner will guarantee the specified reductions.
• Measures should also be considered for control of emissions in inland waterways. The vessels plying in them usually run on gas oil with a low sulphur content (the EU limit, now 0.2 per cent, is to be reduced to 0.1 per cent from 2008). Emissions of NOx are at present high, but could be reduced either by the SCR or the HAM technique.

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To get more information
The situation and proposals for remedying it are described more fully in Economic instruments for reducing emissions from sea transport by Per Kågeson.

Published: January 2002.